Diluent volume for epidural fentanyl and its effect on analgesia in early labor

Epidural fentanyl after a lidocaine and epinephrine test dose provides adequate analgesia and allows for ambulation during early labor. We designed the current study to determine the influence of the diluent volume of the epidural fentanyl bolus (e.g., whether it has an effect on the onset and duration of analgesia). Sixty laboring primigravid women received a 3-mL epidural test dose of lidocaine with epinephrine and then received a fentanyl 100-mug bolus in either a 2-mL, 10-mL, or 20-ml, volume. Pain scores and side effects were recorded for each patient. The onset of analgesia was similar in all three groups. The mean duration before re-dose was not significantly different in the 2-ml, group (108 +/- 40 min), the 10-ml, group (126 +/- 57 min), or the 20-mL group (126 +/- 41 min). No patient in any group experienced any detectable motor block; one patient (2-ml, group) complained of mild knee weakness and was not allowed to ambulate. In early laboring patients, the volume in which 100 mug of epidural fentanyl (after a lidocaine-epinephrine test dose) is administered does not affect the onset or duration of analgesia, nor does it affect the ability to ambulate.